There is also evidence that the ability of patients to use the different inhaler device types is variable. Nonetheless, recent reviews of RCTs, while recognising the importance of inhaler technique, have concluded that inhaler devices do not differ significantly in efficacy and that the cheapest inhaler device should be used. However, as results are based on RCTs they should be applied with care in light of the aforementioned issues around external validity of RCTs and the ability to extrapolate their findings across a broad patient population. Moreover, patients enrolled in RCTs typically receive extensive training and must demonstrate and maintain proper inhaler technique, seldom accomplished in a real-world setting.